Thread: Knapweed changing soil composition

Graduate student says results will help in management of invasive weeds

By Coloradoan staff

Invasive plants not only are changing the ecosystem above ground, but actually are changing the composition of the dirt itself, according to new research conducted by a Colorado State University graduate student.

Invasive plants not only are changing the ecosystem above ground, but actually are changing the composition of the dirt itself, according to new research conducted by a Colorado State University graduate student.

Invasive plants such as spotted knapweed flourish in new environments that lack their natural enemies, such as pathogens that have co-evolved with the invasive species in the original native environment.

"Spotted knapweed originated in Eurasia where it is held in check by pathogens, herbivores and other plant competitors that evolved along side of it," Broz said. "When knapweed was introduced to the American West, it escaped these natural enemies, allowing it to spread and take over many of our native grasslands."

Researchers collected soil samples from areas near Missoula, Mont.; spotted knapweed infests more than 4.7 million acres in the state. In areas with high densities of spotted knapweed, there was 80 percent less DNA of fungi than areas with low-densities of spotted knapweed.

Even areas with a low-density of spotted knapweed showed changes in the amount and types of soil microbes naturally found in the area, Broz said.

Soil microbes can have a profound influence on molecular and biochemical processes in individual plants, plant community and ultimately the entire ecosystem. The disruption of the balance between native plants and microbial communities in the soil can have a negative effect on native plants while benefiting invasive species.

The findings provide more information about the impacts that invasive species can have on an ecosystem, Broz said.

"A better understanding of the interactions between native plants, invasive species and the native soil community will help in developing more effective strategies in managing invasive species and restoring the landscape to its natural state," she said.